The
Yellowstone Volcano could erupt with 10,000 times the force
of the explosion at Mount. St. Helens in 1980. (Photo
Courtesy of USGS and Alan Post)

Is the Super
Volcano Beneath Yellowstone Ready to Blow?

About
4 miles beneath Yellowstone National Park's beautiful scenery
is a forty-mile-wide chamber full of molten rock under incredibly
high pressure. This magma is what powers Yellowstone's fantastic
geysers and hot springs, but is it about to erupt in a cataclysmic
explosion that will decimate the western United States and push
mankind to the brink of extinction?

Yellowstone is the crown jewel of the United States
national park system. Its mountain vistas, wildlife and geographic
features are visited and admired by people from around the world.
More than any of those, however, it's the park's thermo-geological
features that make it unlike any other part of the globe. No place
on earth has as many steam vents, hot springs and active geysers
as Yellowstone.

To create these features requires two elements in
abundance: lots of water and lots of heat. The water is provided
by the generous rain and snow the region gets. The heat comes
from deep inside the earth: volcanic heat. Though you might not
be able to tell from just looking at it, Yellowstone National
Park is built on an ancient volcano. Not just a regular volcano,
either. It lays on top of what some people have started to call
a "super volcano."

Super
Volcanos

There is no exact definition for a super volcano,
but the term is often used to refer to volcanos that have produced
exceptionally large eruptions in the past. When one of these large
eruptions occurs, a huge amount of material is blasted out of
the super volcano, leaving a giant crater or caldera. Such
a caldera can be as much as forty or fifty miles wide. At Yellowstone,
the caldera is so big that it includes a fair amount of the entire
park. In fact, it is so big that scientists confirmed that the
region had a caldera by looking at photographs from space.

Since there is no firm definition of what a super
volcano is, it's hard to say how many of them are found on the
earth. Usually people list Long Valley in eastern California and
Taupo in New Zealand as super volcano sites along with Yellowstone.
The last known explosion of what might be considered a super volcano
was Toba in Indonesia. Toba erupted with a titanic explosion about
74,000 years ago. The force of the explosion was estimated to
be 10,000 more powerful than the blast that destroyed Mount St.
Helens, in Washington. Tremendous amounts of rock and ash were
ejected into the air, blocking the sun for months. The temperature
around the globe was thought to have plummeted as much as 21 degrees.
Perhaps as much as 75% of plant life on the North American continent
may died out.

Old
Faithful geyser, as well as Yellowstone's other geothermal
wonders, is powered by the heart of one of the most powerful
volcanos on Earth. (Copyright Lee Krystek,
2000)

A super volcano differs from a regular volcano in
that there is often no mountain peak associated with it. In a
regular volcano hot magma under pressure flows up from the depths
of the earth. A hole forms in the surface and the magma, now lava,
pours out. As it cools, it forms a cone that eventually builds
up into a mountain. If the passage is blocked off, the pressure
can build up in the mountaintop and explode with a monstrous force.
That's what happened at Mount St. Helens. The pit formed by the
explosion becomes the new caldera.

In a super volcano the magma is blocked from ever
reaching the surface. Instead, the pressure just builds and builds
until more and more rock in the area melts and becomes magma too.
The area under the surface becomes one huge underground sea of
semi-molton rock. Finally, the pressure becomes too much to hold
back and the entire surface above the underground chamber, which
can be many miles wide, is blown away by a titanic explosion that
can be thousands of times more powerful than that of a regular
volcano.

Yellowstone's
Catastrophic Eruption

This last happened at the Yellowstone volcano approximately
650,000 years ago. The caldera that it left is 53 miles long and
28 miles wide. In the area surrounding Yellowstone, 3000 square
miles were subjected to a flow of pyroclastic material composed
of 240 cubic miles of hot ash and pumice. Ash was also thrown
into the atmosphere and blanketed much of North America. It can
still be identified in core samples from as far away as the Gulf
of Mexico.

Since this occurred more than a half million years
ago this is all ancient history, right? Not quite. Yellowstone
continues to be geologically active even today. Smaller explosions
caused by hydrothermal activity (water or steam heated in an underground
chamber until the top blows off) have been much more common and
recent in Yellowstone's history than the massive caldera-forming
eruptions. One of these happened as recently as 13,000 years ago,
creating a three-mile wide crater that is now a portion of Yellowstone
Lake called Mary Bay. Also, smaller volcanic eruptions with flows
of lava, ash and pumice have occurred. Flows like these have filled
in much of the old caldera since its creation.

Another catastrophic eruption is also possible.
The effects of such a disaster are hard to even comprehend. Bill
McGuire, professor of geohazards at the Benfield Greig Hazard
Research Centre at the University College of London told the UK
Daily Express, "Magma would be flung 50 kilometers into
the atmosphere. Within a thousand kilometers virtually all life
would be killed by falling ash, lava flows and the sheer explosive
force of the eruption. One thousand cubic kilometers of lava would
pour out of the volcano, enough to coat the whole USA with a layer
5 inches thick." He adds that it would once again bring "the
bitter cold of Volcanic Winter to Planet Earth. Mankind may become
extinct."

Reasons
to Worry?

Scientists have known about Yellowstone's explosive
history for quite some time, but events in the fall of 2003 suddenly
had people concerned about the possibility of another massive
explosion.

Areas
of the Norris Geyser basin have been closed due to unusual
activity.

In August of 2003 a new high-resolution sonar map
of the bottom of Yellowstone Lake showed a bulge, or "inflated
plain" there that was 2000 feet long and 100 feet high. Was
it being pushed up by hydrothermal or even volcanic forces?

At about the same time there were some unusual changes
at Norris Geyser basin some 20 miles north of the lake. Areas
formally dry suddenly had hot springs. Other hot springs dried
up. A long dormant geyser became active and forced the closing
of some of the trails through the basin.

A report released in December of 2010 further raised
concerns. Scientists published a study in the Geophysical Research
Letters entitled "An extraordinary episode of Yellowstone caldera
uplift, 2004-2010," that showed that the caldera had risen 7 centimeters
a year between 2004 and 2006.

Some amateur geologists connected these events with
the history of the Yellowstone volcano and came to some troubling
conclusions: The catastrophic caldera making eruptions have occurred.
at 2.1 million, 1.3 million and 650,000 years ago. Was another
one about to happen? Was the next explosion overdue? Interest
in these developments quickly mounted. Several Internet sites
sprang up predicting another explosion very soon and suggesting
that the only way to avoid such a disaster was to drill holes
into the magma chamber to release the pressure. In a January 2011
interview City University of New York physicist Michio Kaku said,
"It's black magic trying to predict exactly when it's going to
blow, but we do know one thing: one day it will blow" and "…all
you can do is run."

Conditions
Normal

As fascinating as the history of Yellowstone volcano
is, however, most professional geologists who study the site are
not concerned that the park is on the brink of a catastrophic
eruption. The bulge on the bottom of the lake may have been there
for thousands of years, but not noticed until the recent survey.
Changes in the geyser activity is not unusual. New geysers have
appeared throughout the history of the park, while others go dormant.
Rangers often shut down parts of trails or alter them as needed.

The land near the center of the caldera did rise
more than three feet between 1923 and 1985. However, between 1985
and 1992 it actually subsided six inches. Studies of the shorelines
of Yellowstone Lake have led scientists to believe this is a regular
phenomenon. The caldera floor has risen and fallen at least three
times in the last 10,000 years, moving as far as 65 feet.

An author of the 2010 study,Bob Smith of the University
of Utah, said "At the beginning we were concerned it could be
leading up to an eruption, but once we saw [the magma] was at
a depth of ten kilometers [six miles], we weren't so concerned.
If it had been at depths of two or three kilometers [one or two
miles], we'd have been a lot more concerned."

Yellowstone Volcano Observatory in a statement in
2011 added, "Geological activity over the past five years includes
widespread ground uplift and two notable earthquake swarms. Though
scientifically interesting, such events are common in large caldera
systems like Yellowstone, and are not indicative of an imminent
eruption."

The idea that Yellowstone may be "overdue"
is also faulty. With only three catastrophic eruptions and two
intervals between to go on there is not enough data to say that
another one should be occurring in the near future.

Even if there was, there is little mankind could
do about it. Drilling into the magma chamber to release pressure,
as some have suggested, would be impractical and ineffective.
The material in the chamber has the consistency of a sponge and
any "hole" opened up to the surface would quickly seal
as the molten rock crept up and cooled.

The
Sleeping Dragon

That doesn't mean that there isn't (as one scientist
put it) a proverbial giant dragon sleeping under Yellowstone.
It may well one day awake and lay waste to much of the western
United States. The Yellowstone Volcano Observatory, however, watches
the park carefully and analyzes the continuous geological changes
occurring in the region. It is likely that the imminent threat
of another catastrophic explosion would not go unnoticed by their
modern instruments. So far, however, activity is business-as-usual
at the park.

Still, the super volcano at Yellowstone, and its
kin around the world are a credible threat to man. Even the United
States Geological Survey, usually conservative about such matters,
admits that should a major eruption occur the results would have
"global consequences that are beyond human experience and
impossible to anticipate fully."